Concentration of potash ores containing sylvite



Allg. 5, 1958 w. A. SMITH ETAL f 2,846,068

CONCENTRATION OF POTASH CRES CONTAINING SYLVITE Filed Jan. 14, 1952 UNDER/:LOW j C 6 D MME-UP WML-'R M WASTE I BYM' HTTR/VEY United States Patent O CONCENTRATION F POTASH ORES CONTAINING SYLVITE William Aubrey Smith, Carlsbad, N. Mex., and Vernon L. Mattson and Gene Meyer, Lakewood, and Robert A. Baxter, Golden, Colo., assignors to American Metal Climax, Inc., a corporation of New York Application January 14, 1952, Serial No. 266,314

9 Claims. (Cl. 209-166) This invention relates to the concentration of potash ores containing sylvite and especially to the concentration of potash ores containing mixtures of oceanic salts with clays and of which sylvite and halite are normal constituents. The invention has for a more particular and representative application the separation and concentration of the sylvite values of sylvinite ores which in their naturally occurring state contain small but nevertheless objectionable amounts of insoluble clay-like minerals that interfere with the concentration of the sylvite content of such ores by flotation and other known concentrating procedures. A typical example of sylvinite ores of this type is that found in the Carlsbad district of New Mexico.

It is already known that sylvite can be recovered in the form of a concentrate from suitably ground potash ores suspended in a saturated solution of the soluble constituents of such an ore by froth otation and other methods involving wet stratitication. As has been the case in conventional flotation practice with other ores, it has been recognized that the presence of clay slimes lowers the recovery and otherwise interferes with the operation, and accordingly in concentrating the potash ores by froth otation, tabling and similar procedures it has been customary to subject the ore at a stage in its preparation preceding the concentration step to a mechanical desliming treatment designed to remove as large an amount of the slime as it consistent with an economic operation. However, we have found that the mechanical desliming procedures customarily employed do not bring about a sufciently complete removal of the insoluble-clay minerals to insure a satisfactory commercial grade of concentrate and a satisfactory recovery. Moreover, the consumption of amines and similar collecting agents has remained relatively high.

We have disclosed in our U. S. Patent No. 2,724,499, dated November 22, 1955, a procedure whereby it is possible in concentrating potash ores containing sylvite by the froth flotation method to obtain a high grade of concentration with a satisfactory recovery by treating the ore, in a step preliminary to the conventional amine conditioning step, with a slime control agent having for its purpose to suppress or control the tendency of insoluble clay slime particles present in the pulp to react with the amines customarily used as collecting agents in the otation process or otherwise render them inelective to perform any collecting function.

The present invention has for an object to provide an improvement in the desliming of potash ores wherein a slime dispersing agent having special etfectiveness in dispersing the clay slimes associated with such ores when they are suspended in a brine pulp is employed to facilitate the separation of the insoluble slime particles from the ore values and to promote the effectiveness of a succeeding mechanical desliming treatment applied to the thus treated ore pulp.

It is a further object of this invention to improve the ice ' tion and thereby in like proportion increase the amount of the potash available to the flotation feed.

It is a further object of vthis invention to control the amount of tine potash removedin the desliming operation to approximately that amount which is contained in the normal loss of brine from the circuit, or more specifically that amount which is required to prepare an amount of. This procedure willv make it possible to maintain a constant amount of brine brine equal to these normal losses.

in the circuit.

Other objects and advantages of the present invention:

containingY potash ores are ground and suspended in sat-A urated brine solutions are only imperfectly separated from the pulp by the commonly employed mechanical desliming procedures unless the desliming treatment is repeated many times. Even when the ore is subjected to repeated desliming treatments in excess of those that would be regarded as commercially practical, suicient insoluble slime will remain to interfere with and cut down the efticiency of the collecting agent. i

We have found that whereas Ait is impractical to rely solely upon the use of conventional mechanical desliming apparatus to reduce the slime content of the ore pulp` to a point at which the insoluble slimes cease to interfere with the normal flotation of sylvite by an amine or other suitable collecting agent, it becomes entirely practical to reduce the slime content to such a point by first subjecting the pulp to treatment with a dispersing agent selected from that class of lignin derivatives which consists of the sulfonated lignins and partially desulfonated lignosulfonates and thereafter, while the insoluble slime is in a dispersed state, subjecting it to a suitable mechanical vdesliming treatment. In laboratory tests it was found that even when the pulp had been subjected to as many as seven successive mechanical desliming treatments, Without addition of a dispersing agent of the class above mentioned, there still remained af sufficiently large proportion of insoluble slime to interfere very materially with the eiciency of the flotation. On the other hand, when the ore previously reduced to the desired size for the separation was treated in the form of a pulp with a lignosulfonate dispersing agent and subjected to a preliminary agitating treatment, only two mechanical desliming `operations were required to bring the residual slime down to a percentage lower than that obtained without the dispersant.

In these desliming operations carried on under laboratory conditions the effectiveness of asingle desliming treatment was very considerably lower than what may be realized under full scale conditions with a hydraulic classier, but nevertheless the laboratory tests serve to provide a fair basis of comparison; Under the conditions maintained in the laboratory tests, four deslmings without the dispersant were aproximately equal in their effectiveness to a single full scale desliming operation conducted in a conventional hydraulic classifier. v

In carrying out the desliming tests under laboratory conditions, a weighed sample of ground potash ore was placed in a glass bowl Fagergren otation machine with sucient-water to form a pulp consisting of approximately 32% solids and then agitated. The suspension was allowed to settle for a specied time and then decanted to a specic depth. Repetition of this procedure provided 4 flotation is clearly indicated by comparing the dotation recoveries listed in Tables III and IV. In each case the flotation reagent was 0.159 lb. of amine acetate (Armac TD) per ton of ore. The following tests were carried progressive removal of the remaining slime. In a series out under like conditions in all respects except as to the of'tests carried on without:a'ddition of the dispersant it use of a dispersant. was observed that approximately 90% of the insoluble Table 111 slime is'removed by Yfour desliming operations such as havebeen-described. The amount of slimeiwhich may N b P t be Vremoved-byi:`u1ther repetition of the operation is so 10 Test Number gilde? Rerfiy small that an economlcrllmlt 1s indicated. The data pre- Shmmss of KCl sented in Table I clearly illustrates this point.

No Marasperse Used Table I 3 s s 1 No. of y No. Percent Slime Percent 4 55-9 Deslimmins. Weight Assay, Insol- 5 66. 4 N0.Test Settling Removed Percent uble 5 85-5 Steps Time as Total Inso1- Slime 7 94- 8 v Slime uble Removed No Marasperse CB Used Table IV 2 2 4. 45 18. 72 76. 1 Number Percent 2 5 1. G6 37. 50 42. 5 A'Iest Number of De- Recovery 3 1 7. 4 14. 42 S2. 1 slmings of KCl 4 1 9.5 12. 72 88.6 s` 1 as 13. 4s 93.6 25 6 1 8. 3 15. 80 95. 1 0.5 lbs. of Marasperse CB per ton 0f ore added before desliming 7 1 9.4 14.70 93. 2

Average results.... 6. 99 18. 19 81. 6 3 59. 0 4 89. 4 n c o u 5 891 2 A second senes of tests were earned on under s1m1lar g vggg conditions except that a ligno-sulfonate of the class herenafter described, in the proportion of 0.5 lb. per ton of ore, was added to the ore before the initial agitation step, whereupon the pulp was subjected to repeated decantation .and agitation steps as in the corresponding tests referred to in Table I. The eiect of the addition of the 4dispersant is illustrated in Table II.

Table II No of No. Percent Slime Percent Deslimmins. Weight Assay, Insol- *No Test lng v.Settling Removed Percent uble Steps Time as Total Insol- Slime Slime uble Removed 0.5 lbs. per ton Marasperse CB used before desliming Average Results.-- 4. 69 27. 85 85. 8

Table I indicates that an average of 6.99% or 139.8 lbs. of slime per ton of ore was removed when no dispersant was used. This slime contained 18.19% or 24 lbs. of insoluble slime particles.

When Marasperse CB was used as a dispersant only 4.69% or 93.8% lbs. of slime per ton of ore was removed. This slime fraction, however, contained 27.85% of insoluble material while that removed without the aid of a dispersant contained only 18.19% insoluble material. A total of 26 lbs. of insoluble slime was removed when a dispersant was used as 'compared to 24 lbs. when no dispersant was used. This comparison indicates two advantages in the use of a dispersant.

(l) A higher removal of insoluble slime.

(2) Less fine potash is lost in the decanted liquid when a dispersant is employed.

The importance of item two in this comparison is evident when it is pointed out that 40l lbs. of additional soluble salts are available to dotation feed when a dispersant is used.

The eiect of mechanical removal of slime before The flotation time in all tests was three minutes. In all cases recovery improved as the percentage of slimes was reduced. It is significant that when no dispersant was used six deslimingl operations were necessary to make 85.5% recovery possible, while only four deslming operations with a dispersant resulted in a recovery of 89.4%. These tests conclusively indicate the value of the dispersant in aidingthe mechanical removal of the insoluble slime particles.

Although as Yabove indicated, it is possible with the use of the special typel of dispersantin conjunction with use of conventional mechanical desliming apparatus to reduce the percentage of insoluble slime to a point where a high grade concentrate and Aa satisfactory recovery of the potash ores may be obtained in a subsequent concentration operation, it is frequently more economical when employing the froth flotation process as the concentration step to discontinue the desliming treatments when the content of insoluble slimes has been reduced to a very considerable degree but still sufficient of the insoluble slimes remain to require further treatment before adding a collecting agent.

From the data presented above, it is shown that when one of thelignosulfonates of Vthe class mentioned is used, it is possible 4to reduce the slimes to a point Where chemical control of the remainngslime is practical. It is also possible by this method to reduce loss of soluble potash slime to a minimum. With the insoluble clay slimes reduced to such a point it Will be frequently more economical to discontinue the desliming operation at this point and then treat the ore pulp with a sucient amount of a slime control agent such as starch, or preferably a polyglycol or a polyglycol ether as described more particularly in our aforesaid Patent No. 2,724,499, to Suppress the ltendency of the remaining insoluble slime constituents to react with the amines or other collecting agents employed to prepare the pulp for the froth iiotation concentration.

For convenience there is set forth in the attached drawing a -ow sheet illustrating in full lines one simplilied form of -the process. Certain modifications of the procedure are indicated in dottedlines. It will be understood by those skilled in the art that many variations in the procedure may be made without departing from the invention.

According to one procedure for carrying out the invention, run of mine ore is rst subjected to dry crushing to The ore is then pulped with a saturated brine composed of the sylvite and halite constituents of the ore. A suicient quantity of the ligno-sulfonate dispersing agent is added, preferably along with the brine, to insure the desired dispersing action on the slime. The pulp is then passed through a scrubber which may consist of a rotary drum carrying lifts for tumbling and mixing the ore and brine. Sufiicient brine is added at or immediately ahead of the scrubber to produce a pulp containing from 60 to 70% solids. The pulp is passed from the scrubber to a classifier where additional brine is added. The operating conditions at the classifier are advantageously so regulated as to insure that the overflow shall consist of a pulp containing ore particles of suitable iineness for a otation feed, for example, a fraction composed principally of particles passing through a mesh sieve. The underow consisting principally of the coarser particles in the form of a thick pulp, say 60% solids, is then diluted with additional brine to a suitable density for Wet grinding, say to about solids, and then subjectedto wet grinding to reduce such coarser ore particles to a suitable ineness for the flotation feed. The pulp containing this ore fraction is then combined with the fraction of similar iineness from the classifier overflow and fed to a second classifier of a type suitable for slime removal. lf necessary a further quantity of the lignosulfonate dispersant may be added to the pulp as it is being fed to the second classifier. The rates of feed and agitation as well as other classification conditions are so regulated as to insure an overflow which contains largely 270 mesh particles of the ore and the insoluble slimes. The underow containing the rest of the ore may be fed directly to a conditioner where an amine or other suitable collecting agent is added. Ordinarily, it will be preferable to pass the pulp successively through at least two conditioning steps, in the first of which the pulp is thoroughly mixed with a regulated amount of a slime control agent of the type of starch, a polyglycol or a polyglycol ether and in the second it is mixed with the collecting agent or agents in sufficient amount to insure the desired collecting action. The thus conditioned pulp, after adjustment of the density by adding more brine if necessary, is then fed to a `flotation machine and oated.

The mechanical desliming treatment may be repeated one or more times before leading the pulp to the iirst conditioner by providing two-or more classifiers in series. lt will be understood that, other things being equal, the greater the number of desliming treatments the less need there will be for the use of a slime control agent such as a polyglycol in the subsequent conditioning stage of the preparation of the ore for the flotation concentration. Generally, however, it will be preferable to provide a preliminary conditioning step in which a regulated amount of a slime control agent such as one of the polyglycols or a polyglycol ether is added preliminary to the addition of the collecting agent. This offers greater insurance against variations in the grade and in the recovery due to variations in the insoluble slime content of the ore.

It is generally more economical to provide a controlled smallV addition of a. polyglycol or a polyglycol ether slime control agent than to repeat the mechanical desliming treatments to a point where a substantially complete removal of insoluble slime is insured. Likewise, it is more economical to provide sufiicient of the lignosulfonate dispersant to insure a satisfactory dispersion of the slimes of the pulp as it is brought to the mechanical desliming step of treatment in a classifier than to multiply the classifications.

A further important advantage that is realized by minimizing the number of mechanical classifications resides in the fact that less Water is required for .the brine circuit.

This is a factor of considerable importance both from the standpoint of the cost of maintaining facilities for brine storage and also from the standpoint of operating costs for pumping equipment and power, and even for Water itself. Our process makes it possible to maintain a Water and brine balance with greatest possible conservation of ore values.

It is a still further important advantage of the process that the use of the lignosulfonate dispersant increases the recovery of the sylvite directly in the iiotation concentration operation and reduces the amount of sylvite that would otherwise be carried off in the overflow from the classifiers entrapped with the slime particles and lost to the process unless recovered by resort to the relatively expensive recrystallizing operations.

The lignosulfonates are a class of lignin derivatives produced in the form of their salts by fractional precipitation from waste liquors resulting from the treatment of wood pulp in paper manufacture. The lignosulfonates used as dispersants in the process of the present invention are preferably used as the alkali and alkaline earth metal salts. Examples of these salts that have been found to be suitable dispersants for the insoluble slimes contained in potash ore brine pulps are the sodium and calcium salts of lignosulfonic acid containing either a single lignin group, i. e., the monomer, or polymers of the simple lignin molecule with a molecular weight up to about 20,000. Best results have so far been obtained with the lignosulfonates of lower molecular weight within the above stated range. It also appears that the lignosulfonates lthat have been partially desulfonated have a stronger dispersing action under the brine conditions which exist in this process than those having a higher proportion of sulfur.

For example, the product known commercially as Marasperse CB and sold by the Marathon Chemical Company, of Rothschild, Wisconsin, has proven to be very effective in its dispersing action under the conditions hereinbefore outlined. This product is understoodto be a sodium salt of a partially desulfonated' lignosulfonic acid having a sulfur to lignin ratio of about 32- to 1900-2000. This product is understood to contain about of the lignosulfonate. Other compounds obtained from the` above source and shown to be effective as dispersants in our process are the products known as Marasperse C, containing about 76% of calcium lignosulfonate in a partial state of desulfonation; Marasperse N, containing about 76% of sodium lignosulfonate and having a sulfur tolignin ratio of about 32 to 440; and Maracell E, con` sisting principally of sodium lignosulfonate desulfonated to a sulfur to lignin ratio of about 32 to 2500.

The following flotation test results are submitted in support of our conclusions concerning lthe utility of the lignosulfonates as aids in the concentrations of potash ores containing sylvite and the role they play in such operations when they are properly used as desliming agents. The flotation tests were conducted under identical conditions with sylvinite ore obtained from the Carlsbad district of New Mexico.

ln conducting the desliming operations the following standard procedures were followedy except as they were modified in specific tests by the additionof one of thelignosulfonate dispersants either before or after the' mechanical desliming operations as specified.

Our investigations have indicated that substantially all: the objectionable insoluble slime is removed frornthe ore samples by screening the ore in the form of a saturated brine pulp at 270 mesh. Therefore, this procedure was followed in making the desliming determinations.

The desliming operations consisted of the following standard procedures:

(l) A 1200 gm. sample of dry, -14 mesh ore is weighed.

(2) This sample is pulped with fully saturated brinef (KCl and NaCl) in a standard Fagergren` 3-lit'er labora#` tory flotation machine. The pulp is brought to a predetermined level markabout 2" below the top of the bowl.

(3) The cell is agita-ted at standard operating speed for minutes. (Note: In all subsequent desliming steps this time is reduced to 1 minute.)

(4) The pulp is permitted to settle for two minutes after the agitation period.

(5) The suspended slime and brine is then siphoned to a depth of 4% from the top of the bowl.

The following procedure was used to determine the pounds of insoluble -270 mesh `material per ton of ore in the sample after any given number of desliming operations:

(1) Two hundred grams of deslimed `ore resulting from step 5 above is removed from the cell.

(2) This 200 gm. sample is screened over a 270 mesh screen. The screen undersize is then leached to remove all water soluble constituents. The insoluble portion is then dried and weighed. From this weight the percentage of insoluble slime is calculated.

(3) To lobtain the percentage of KCl recovery the remaining 1000 gm. from step l of the previous procedure is floated with 0.159 lb. of Armac TD per ton of ore for three minutes.

The results of comparative tests carried on under identical conditions, except as to the addition of Marasperse CB, are set forth in the following table:

A standard iiotation test was run on each sample using 0.159 lb. of Armac TD and 0.001 lb. of Dupont Frother BX23 per ton of ore.

Armac TD is an amine collecting agent sold by Armour & Co. and understood to consist of the water-soluble acid salts of the normal hexadecyl, octadecyl and octadecenyl amines in the approximate proportions of 30, 25 and 45 parts by weight.

- Dupont Frother B-23, hereinafter sometimes referred to as Et-23, is a commercial product of the Dupont Company commonly used in the flotation art as a frothing aid and Ifroth moditier. It is understood to consist of 40-45% of primary alcohols (principally 2,4-dimethyl pentanol-l), 45-50% of secondary alcohols (principally 2,4-dimethyl hexanol-3), and 8-12% of unidentited ketones.

It will be observed from the results of the tests set out in Table V that the recovery of KCl increased very strikingly when the lignosulfonate had -been added priliminary to the desliming treatment (test 265) and that the percentage of residual insoluble slime was substantially reduced as compared with the amount present in the flotation feed when no lignosulfonate was added before the desliming treatment or the lignosulfonate was added after the desliming treatment.

It will be observed further that the proportion of KCl recovered in the concentrate was very much lower when the .lignosulfonate was added after conclusion of the desliming treatment than was the case when it was added preliminary to the desliming treatment. The influence of residual insoluble slime is also indicated by differences 8 in the results obtained in tests 266I and 267 which were carried on under similar conditions.

The same striking differences were observed with variation of the extent to which the mechanical deslirning was carried. This is brought out in the following table:

Table VI Percent KCl Percent KCl Test Preliminary Desliming Assay Distribution No. Treatment Conc. Tails Cone. Tails 271 Pilot desumed 5 03.1 17.7 66.43 33.51 272 0.50 lbs. Mar. GB per t0n ieed;thendeslimed 5 95.11 6.1 89.20 10.80 273-... Deslimed 5X; then 0.50 lbs. Mar. CB added per ton feed 96.5 29.7 30.0 64.00

As further showing that the recoveries were consistently better when the addition of the lignosulfonate preceded the desliming treatment as compared with the results obtained when it is added at a later stage, there are set out in the following table the yresults of comparative tests that were conducted under conditions involving prolonged desliming treatments:

Table VII Percent KCl Percent KCl Lbs. Test Preliminary Deslim- Assay Distribution Insol. No. ing Treatment Slime perton Conc. Tails Conc. Tails feed 299.-- Deslimed 6X; then Mar. B added 0.501bs./ton ore 95.5 30.1 32.9 67.1 2.01 300-.- Mar. CB 0.50 lbS./ ton were added; than deslimed 0X. 93.2 4.2 93.0 7 2. 90 301. Deslimed 6X; then Mar. CB added 0.501bs./ton ore--- 95.8 23.2 54.4 45.0 1.94 302..- Mar. CB 0.50 1bs./ ton was added; then deslimed 6X. 95.4 2.7 95.6 4.4 3. 04

The following tests were conducted for the purpose of evaluating the advantages that may be derived by using lignosulfonates as aids in the preliminary desliming treatment carried only to an intermediate stage followered by addition of a slime control agent as the conditioner in advance of the addition of the collecting agent or agents:

Table VIII Slime Control Percent KCl Percent KCl Agent Addi- Assay Distribution Test N0. tions Following Partial Desliming Conc. Tails Conc. Tails 0.50 lbs. Marasperse GB per ton of ore added before partial desliming In tests Nos. 75, 79, and 81 the mechanical desliming treatment was carried on in a standard Fagergren three-liter laboratory flotation machine in a similar manner as described hereinbefore for the tests previously mentioned in this application except that in each instance a 1000 gram sample of -20 mesh sylvinite ore was used. After the ore was pulped and combined with Marasperse CB in the proportion of 0.5 lb. per ton of ore, the pulp was agitated by rotating the bowl at a standard operating speed for ve minutes as in the previously described tests. The pulp was then allowed to settle for two minutes and the suspended slime and brine was then siphoned to a depth of 4% from the top of the bowl.

This desliming operation was repeated three times with the agitation period reduced to one minutein the second and third desliming steps.

Following the desliming treatment the deslimed product of tests Nos. 75 and 80 was conditioned for the otation operation by iirst adding a 2% solution of pearl starch to the pulp in the proportion of 0.4 lb. of starch per ton of ore, then conditioned Ifor three minutes. Thereafter Armac T and Nonic 218 in the proportions of 0.14 lb. Armac T and 0.05 lb. Nonic 218 per ton of ore were added and the pulp was further conditioned for 40 seconds. The thus conditioned pulp was then subjected to dotation under standard operating conditions. The same procedure was followed in tests Nos. 79 and 81 with the same kin-ds and proportions of collecting agents but without any addition of starch.

Armac T is an amine collectin-g agent manufactured by Armour & Co. Nonic 218 is manufactured by Sharples Chemical Co. and is understood to consist principally of polyethylene glycol tert. dodecylthioether. It was added as a frothing agent.

There are set out in the following table the results of a series of desliming tests made with other lignosulfonates to compare their value with Marasperse CB. In each test a 500 gram sample of ground ore was agitated with saturated brine in the glass bowl of a Fagergren flotation machine with 0.5 lb./ton of the particular reagent being tested. When agitation was stopped the pulp was allowed to settle for ve minutes and the brine and suspended slime was then removed by decantation to a depth of 41/2 inches from the top of the bowl. Removal to this depth permitted approximately one inch of brine to remain over the settled solids. The bowl was again filled with saturated brine to the overflow of the bowl and agitated for one minute, then allowed to settle for ve minutes and decanted to the level described above. This operation was again repeated. The decanted portions from the three desliming operations were combined and the amount of insoluble slime contained therein was determined.

It will be seen from the above table that all of the lignosulfonates tested show value as dispersants of the insoluble slime content of sylvinite potash ore, and also substantially increased the proportion of slime removed from such ores in a subsequent mechanical desliming treatment as compared to the proportion removed by merely subjecting the ore pulp to a similar mechanical desliming treatment without addition of any of the lignosulfonates.

The product identied as NAL-153 in the above table is identied by the manufactures, Marathon Corporation, as a laboratory product not as yet commercially available consisting principally of lignosulfonates that have been subjected to an acid precipitation and only require dissolving in caustic to render them available for use.

Although the invention has been described with particular reference to the use of the improved desliming treatment in connection with a concentration separation treatment involving the use of froth flotation, it will be understood that it is capable of general application in 10 connection with any of the conventional lforrn's of wet stratifying concentration processes applicable to the treatment of potash ores which contain sylvite. Among other concentration procedures to which the invention is particularly applicable mention is made of skin flotation and agglomeration tabling, and procedures involving the use of heavy media or the so-called sink and float principle.

It is to be understood that the examples set forth herein are merely illustrative of the invention and that, within the scope of the appended claims,` the invention may be practised in various other ways that will readily suggest themselves to the person versed in the art.

We claim:

l. The improvement in the concentration of sylvite from potash ores containing sylvite in association with minor but objectionable amounts of clay and similar. slime-forming constituents, which comprises grinding the ore to within the maximum size range desired for the separation treatment, suspending the ore in a saturated aqueous brine solution of the soluble ore constituents, adding a lignosulfonate in an amount suicient to disperse the slime-forming constituents in the resulting pulp, agitating the pulp under scrubbing conditions to free the surfaces of the sylviteparticles from occluded slime particles, adding additional brinek to dilute the pulp suiciently to render it amenable to a wet classification treatment, thereafter subjecting the pulp to a wet classifying treatment to recover the ore separately from the slimes and the dispersing agent, and thereafter reforming the ore into a pulp of suitable density for the concentrating separation treatment and then subjecting the mixture to a concentrating separation treatment to recover the sylvite.

2. The process according to claim 1 wherein an addition of the lignosulfon'ate is made to the ore at a stage in advance of the final grinding step, and a second addition of the lignosulfonate is made afterl the nal grindstep and before the Wet classifying treatment.

3. The process according to claim 1 wherein following the desliming treatment the ore is reformed into a pulp of suitable density for a froth otation concentrating operation, then conditioned with a suitable collecting agent and thereafter subjected to a froth flotation concentration.

4. The process according to claim 3 wherein after the desliming treatment and preliminary to the concentrat- -ing operation, the ore is treated with a slime control agent in an amount suicient to inhibit reaction of any residual slimes with the collecting agent, and the ore is thereafter conditioned for a froth flotation separation by treatment with a suitable collecting agent and is finally subjected to a froth flotation separation.

a 5. The process according to claim 4 wherein starch 1s used as the slime control agent.

6. The process according to claim l wherein after the desliming treatment and preliminary to the concentrating treatment, the ore is treated with a slime control agent selected from the group consisting of the polyglycols and the polyglycol ethers in an amount suicient to inhibit reaction of any residual slimes with an amine collecting agent, and the ore is thereafter conditioned for a froth flotation separation by treatment with an amine collecting agent and is iinally subjected to a froth flotation separation.

7. The process of desliming potash ores containing sylvite in association with minor but objectionable amounts of clay and similar slime-forming constituents to prepare the ore for a subsequent separation treatment to recover the sylvite which comprises reducing the ore to the desired maximum particle size range for the separation, then adding a lignosulfonate to the ore in a proportion suii'icient to insure dispersion of the undispersed slimes present therein, scrubbing the ore in the presence of said lignosulfonate and suicient brine to form a relatively thick pulp, adding additional brine to dilute I1 the" pulp suicientlyto render it amenable to a wet classiii'cation. treatment, and thereafter subjecting the ore to a wet classifying treatment torecover the ore largely freed from the brine as an underow while withdrawing the brine and the slimesas an overiiow.

8. The process of desliming potash ores containing sylvite in -association with minor but objectionable amounts of clay and similar slime-forming constituents to prepare the ore for a subsequentv separation treatment torecover the syluite, which comprises adding a lignosulfonate to the ore at av stage in its preparation for the separation treatment inv advance of the inal grinding step, scrubbing the ore in the presence of said lignosulfonate and suicient brine to form a relatively thick pulp, then adding additional brine to dilute the pulp suficiently to render it amenable to a wet classification treatment, passing the underow to a rod mill and grinding the ore contained therein to the size desired for the separation treatment, adding additional brine to re-dilute the'pulp to a pulp density suitable for a Wet classification treatment, adding additional lignosultonate to the pulp intermediate the grinding and the subsequent wet classitication treatment, and thereafter treating the ore in a wet classifier to recover the ore largely freed from the brine as an underiiow while withdrawing the brine and the slimes as the overflow.

9. The process of desliming potash ores containing sylvite in association with minor but objectionable amounts of clay and similar slime forming constituents to prepare the ore for a subsequent separation treatment to recover the sylvite, which comprises adding a lignosulfonate to the ore at a stage in its preparation for the separation treatment in advance of the final grinding step, scrubbing the ore in the presence of said lignosulfonate and sufficient brine to form a relatively thick pulp, then adding additional, brine' to dilute the pulp suciently to render it amenable to a wet classification treatment, subjecting the dilutedl pulp to a classiication treatment to separate the coarser particles from those of desired size for the subsequent sylvite separation treatment, subjecting the coarser fraction to a further grinding treatment to reduce the coarser particles to the acceptable size' range, combining the tine fraction produced in the: classication step with the ground fraction, adding sutlicient lignosulfonate to complete the dispersion ofthe slime constituents, and thereafter subjecting the ore to a further Wet classifying treatment to recover the ore largely freed from the brine as an underflow while Withdrawing the brine and the slimes as an overflow.

References Cited in the tile of this patent UNITED STATES PATENTS 1,106,630 Darrow Aug. 11', 1914 1,519,019 Boylan Dec. 9, 19724 2,214,716 Breerwood' Sept. 10, 1940 2,238,439 Bishop Apr. 15, 1941 2,288,497 Tartaron et al June 30, 1942 2,289,527 Tartaron et al. July 14, 1942 2,330,158 Tartaron Sept. 21, 1943 2,355,365 Cole Aug. 8, 1944 2,362,432 Cahn Nov. 7, 1944 2,569,672 Jackson Oct. 2, 1951 2,611,485 Tveter Sept. 23, 1952.

OTHER REFERENCES Taggart, Handbook of Mineral Dressing, 1945, section 10, page 08. Y v

Taggart, Handbook of Mineral Dressing, 1945, sec- 5 tion 12, page 22. 

1. THE IMPROVEMENT IN THE CONCENTRATION OF SYLVITE FROM POTASH ORES CONTAINING SYLVITE IN ASSOCIATION WITH MINOR BUT OBJECTIONABLE AMOUNTS OF CLAY AND SIMILAR SLIME-FORMING CONSTITUENTS, WHICH COMPRISES GRINDING THE ORE TO WITHIN THE MAXIMUM SIZE RANGE DESIRED FOR THE SEPARATION TREATMENT, SUSPENDING THE ORE IN A SATURATED AQUEOUS BRINE SOLUTION OF THE SOLUBLE ORE CONSTITUENTS, ADDING A LIGNOSULFONATE IN AN AMOUNT SUFFICIENT TO DISPERSE THE SLIME-FORMING CONSTITUENTS IN THE RESULTING PULP, AGITATING THE PULP UNDER SCRUBBING CONDITIONS TO FREE THE SURFACES OF THE SYLVITE PARTICLES FROM OCCLUDED SLIME PARTICLES, ADDING ADDITIONAL BRINE TO DILUTE THE PULP 